Manufacture of twist-drills



UNITED STATES PATENT OFFICE.

FRANK E. VHITNEY, OF MELROSE, MASSACHUSETTS.

MANUFACTURE OF TWIST-DRILLS.

SPECIFICATION forming part of Letters Patent No. 341,084, dated May 4, 1886.

Application filed January .29, 1885.

Serial No.15-1.30l. (No model.)

Be it k uown that I, FRANK E. WHITNEY, of I Melrose, in the county of Middlesex and State of Massachusetts, a citizen of the United States, have invented anew and useful Improvement in Drills, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming a part of this specificationin explaining its naturem The invention relates to the class of drills known as twist-drills.

Referring to the drawings, Figure 1 represents in plan, and Fig. 2 in end elevation, the blank from which the drill is made. Fig.3 shows in plan, and Fig. 4 in end elevation, the shape to which the blank is first reduced. Fig. 5 is a plan, and Fig. 6 an end View, rcpresenting the shape of the blank after asecond shaping. Fig. 7 is a plan, and Fig. 8 an end view, of the complete drill; and Figs. 9 and 10 show in section modifications hereinafter referred to.

In the manufacture of my improved drills. I first form wire blanks a of the proper length and size. The blanks are then cold-rolled from shank a to point, whereby the section a is reduced in size, as represented in Fig. 3. The end a of the blank is then severed, say, from one-quarter to three sixteenths of an inch back. The section a of the blank is then further reduced by cold-rolling or by swaging, so as to form a shape, a, which is fiattened, as represented in Fig. 6. The shank a remaining of the same size, the blank is then submitted to the operation of a twisting device, whereby the parta is cold-twisted, (see Fig. 7,) and the point is then formed bygrinding.

The complete drill has the shank a, which is the full size of the blank before shaping, and a twisted section made from the drawn or reducedpart of the blank, and is therefore provided with a large shank, whereby it may be firmly grasped or held, and a stiil, tenacious, and strong working-section.

In lieu of forming the blank to the shape represented in Fig. 6, I may c0ld-roll in the flattened blank the grooves or depressions b, so that the blank before twisting shall have either the cross-section represented in Fig. 9 or that shown in Fig. 10. For the larger form of drills perhaps this construction may be desirable, as it reduces the thickness of the metal at the center or portion of the drillblank which forms the point of the drill.

For certain kinds of drills, especially for drills having a sharp pitch, it will be desirable to anneal the blank before it is twisted, in which case of course itis hardened after the twisting operation. a drill by cold rolling and twisting provides a cheap, quick, and economical process for making a very superior drill, as the drill thus formed has all the advantages which come from working metal cold rather than hot, and at the same time enables a com parati velylarge shank to be obtained. It has increased strength, because more rigid. It has a more uniform twist, because when twisted all parts are of the same diameter, and of course offer uniform resistance to the twistingnut. There is also no waste of stock, as all the metal, excepting the end, is utilizedin formingthe drill.

The drill shown in Fig. 7 is especially ap plicable for wood-work and small drills, and

as the reduced part of the blank is of substantially the same thickness throughout, and as the edges are rounded, I am enabled to obtain a very stiii and strong construction in a lighter small drill.

Having thus fully described my invention, I claim and desire to secure by Letters Patent of the United States- The process of manufacturing drills consisting in forming a blank, reducing or ilattening a portion of the blank by cold-rolling, and then cold-twisting said portion, all substantially as and .for the purposes described.

FRANK E. I-IITNEY.

Vitn esses:

J. M. DOLAN, FRED. B. DOLAN.

This process of making 

